The operational reliability of on-board power systems in known vehicles is largely ensured through the provision of plural autonomously operating energy sources, which provide hydraulic and/or electrical energy or power in a constant manner to the power consuming devices of various safety-critical energy systems installed within the power system of the vehicle. Namely, such critical components or systems installed in a vehicle include the hydraulic operating systems for controlling the vehicle, such as steering and braking systems, and various electrical or electronic systems including the electrical power management system and a computer system for navigation, communication, and/or control of the vehicle. Such fail-safe hydraulic and electrical on-board energy systems of a conventional type generally comprise plural, redundant, independent energy sources such as electrical generators or hydraulic pumps that are arranged on or connected to each of the engines of the vehicle, as well as a distribution system primarily including an alternating current (AC) bus and hydraulic network into which the power is respectively provided by the generators and pumps. Various particular system configurations of the above-mentioned electrical and hydraulic on-board energy systems are known, and will now be described in connection with FIGS. 1, 2, and 3, which are simplified schematic circuit diagrams.
FIG. 1 shows a schematic circuit diagram of one conventional system of the above-described type, which is typically used as an on-board energy system in a vehicle such as an air-craft having four engines (1A', 1B', 1C' and 1D'). Each one of the engines has connected or integrated therein an integrated drive generator or IDG (2A', 2B', 2C' and 2D') including a respective three-phase AC generator and an integrated constant speed drive train or transmission. In normal operation, the generators (1A', 1B', 1C' and 1D') generate and provide electrical energy into the respective AC bus bars (3A', 3B', 3C' and 3D') connected thereto. In the event of a failure of one or more of these engines (1A', 1B', 1C' and 1D') or one or more of the integrated drive generators (2A', 2B', 2C' and 2D'), the only available corrective course of action is to disconnect or isolate the inoperative generator (2A', 2B', 2C' and 2D') from the respective effected AC bus (3A', 3B', 3C' and 3D') by means of a bus disconnect switch (4A', 4B', 4C' and 4D') respectively interposed between the generators and the bus bars.
The generator-supplied main bus bars (3A', 3B', 3C' and 3D') are connected together by means of a further one or more cross-connect bus (5') that is connected to each of the main buses (3A', 3B', 3C' and 3D') by a respective disconnect switch (5A', 5B', 5C' and 5D'). In this manner, in the event of an engine failure or generator failure, the essential electrical power consuming devices can be cross-supplied with electrical power through any one of the still-functioning AC buses (3A', 3B', 3C' and 3D') via the corresponding respective disconnect switches (5A', 5B', 5C' and 5D') and the cross-connect bus (5').
Moreover, such known on-board energy systems conventionally include at least one device that operates as an emergency power generator. Such devices typically include a constant speed motor generator (CSMG) (6) that converts hydraulic energy to electrical energy, which is then provided into an AC bus for supplying electrical energy to the especially critical or essential power consuming devices. In the system shown in FIG. 1, a ram air turbine (RAT) (7'), or available hydraulic power on the hydraulic system (10B), drives the constant speed motor generator (6'), which produces electrical energy and provides this energy to the critical or essential AC bus (AC ESS) (3E'). More generally, the primary energy for driving the CSMG emergency power generator is hydraulic power that can be extracted from any one of the three hydraulic systems (10A', 10B', and 10C') of the overall power system. This hydraulic power is provided into the three hydraulic systems by the engine driven hydraulic pumps (9A', 9B', 9C' and 9D') or the ram air turbine (7'). The generation of electrical emergency power by the emergency generator is definitively triggered by a multiple system failure, for example a failure of all generators connected to the engines, various combination failures of engines and generators, a temporary failure of all four engines, or the like. In order to provide a further source or route for providing emergency power in the event of such individual failures, the system includes an additional redundancy or safety bus (5F') that is connectable to at least two of the AC buses (3B' and 3C') through a multi-path switch (8'), so that emergency power may be provided from the critical or essential bus (3E') to the two buses (3B' and 3C') or vice versa in an emergency situation.
As mentioned above, the hydraulic on-board energy system of the vehicle includes three independent hydraulic systems (10A', 10B' and 10C'), among which two of these systems (10A' and 10C') are each primarily or exclusively hydraulically pressurized by one respective hydraulic pump (9A' and 9D') connected to and driven by the respective engines (1A' and 1D'). Generally, these pumps (9A' and 9D') are constant pressure regulated pumps. The third hydraulic system or circuit (10B') is hydraulically pressurized by two pumps (9B' and 9C') respectively connected to and driven by the two engines (1B' and 1C'). In order to be able to make due with a minimum of hydraulic energy in the emergency situation of a multiple failure of engines and/or engine-driven hydraulic pumps, a hydraulic pump connected to or incorporated in the ram air turbine (7') provides hydraulic energy to at least one of the independent hydraulic circuits (10A', 10B', 10C') as generally represented by the connection of hydraulic circuit (10B') to the pump of the ram air turbine (7').
Further connected to each independent hydraulic system (10A'10B' and 10C') are respective pressure regulated hydraulic pumps (11A', 11B', 11C' and 11D'), which are respectively driven by a corresponding electric motor, typically an asynchronous AC motor, which in turn is electrically powered from one of the electrical buses. Generally, these additional electric motor driven hydraulic pumps (11A', 11B', 11C' and 11D') serve to provide hydraulic power to the hydraulic system when the engine-driven hydraulic pumps or even the engines themselves, individually or altogether, are not operating, for example when the air-craft is parked, or especially also during maintenance work and test operations. However, with appropriate circuit interconnections, these additional hydraulic pumps also serve to boost the available hydraulic power in normal operation of the vehicle during periods of high hydraulic power demands, or to provide hydraulic power to the respective circuit in the event of failure of the corresponding respective engine-driven hydraulic pump. This situation is very relevant in practice especially for two of the independent hydraulic systems (10A' and 10C') which are only equipped with or powered by a single respective engine-driven hydraulic pump.
Moreover, a hydraulic power transfer unit PTU (121') can be connected to the hydraulic systems, and particularly interconnected between two of the respective hydraulic systems. Such a hydraulic power transfer unit can be used in addition to or as an alternative to the above discussed installed additional electric motor driven hydraulic pumps (11A', 11B' and 11C'). Such a power transfer unit serves for the bi-directional cross-supplying of hydraulic power from one of the independent hydraulic systems having a power surplus to another one of the independent hydraulic systems having an insufficient power supply, for example at a lower pressure or at a lower supply flow rate, or for an increased power requirement.
Finally in the schematic circuit of FIG. 1, respective transformer-rectifier units (TRU 1' and TRU 2') serve to transform and rectify the respective AC power provided by the two engine-driven AC generators separately to the respective AC buses (3A' and 3D'). Thus, the individual transformer rectifier units (TRU 1' and TRU 2') respectively and independently provide DC power onto two DC buses (DC bus 1' and DC bus 2').
Two further typical on-board energy systems relate or apply to a vehicle having two engines, which will respectively be described in connection with FIGS. 2 and 3. In each case, each of the two engines of the vehicle has connected thereto an integrated drive generator including an AC generator and an integrated constant rotational speed drive train. The integrated drive generators respectively provide electrical energy to corresponding AC buses in the normal operation condition. The two systems of this type that will be described in the following each respectively have three independent hydraulic circuits or systems, but only have two engines and two AC buses, in comparison to the above system configuration having four engines and four AC buses. Furthermore, both of the following systems comprise essentially the same components in the way of hydraulic pumps, engine-driven generators, ram air turbine driven hydraulic pumps, emergency power generators, etc., while these various components are simply interconnected in different circuit arrangements in the two following systems in order to supply respective power to the three independent hydraulic systems and the two AC buses as well as the safety or essential AC power bus.
In view of the above, FIG. 2 shows a known system in which each of the two engines (1A" and 1B") respectively drives two hydraulic constant pressure regulated primary pumps (9A" and 9B"; 9C" and 9D") as well as a main generator (2A" and 2B"). Furthermore, the hydraulic systems respectively comprise an electric motor driven constant pressure pump (11A", 11B" and 11C") for providing hydraulic power while on the ground (i.e. while the engines of the air-craft are not operating), as well as at least one pump driven by a ram air turbine (7") for providing emergency hydraulic power. Two AC buses (3A" and 3B") are respectively connected to and supplied with power from the engine driven generators (2A" and 2B"), and a cross-connect bus (5") is selectively connectable between the two main buses (3A" and 3B") by means of a disconnect switch (5A"), in order to cross-connect electrical power from one of the main buses to the other in the event of failure of one of the main generators.
The AC power available on the AC buses (3A" and 3B") is further converted and rectified by two transformer rectifier units (TRU 1" and TRU 2") into DC power that is provided to two DC buses (3C" and 3D"). A further AC safety or essential bus (3E") is provided to supply AC power to the critical or essential devices in an emergency situation, from either one of the AC buses (3A" and 3B") through a multi-path switch (8"). In the event that both of the main generators (2A" and 2B") fail, the emergency or safety bus (3E") is provided with power from an emergency power generator CSMG (6"), which produces the electrical power using hydraulic power from the main or central hydraulic system (10B"). In the event of a complete engine failure or a combination failure of one of the engine-driven hydraulic pumps and the other or second engine, then an emergency hydraulic pump coupled to a ram air turbine (7") can provide emergency hydraulic power to the central hydraulic system (10B") and therewith also generate emergency electrical power through the CSMG (6").
FIG. 3 schematically shows a third and final variant of a known system for a vehicle having two engines (1A'" and 1B'"), which has a system architecture generally similar to that of FIG. 2. The essential differences in comparison to FIG. 2 are that each engine only drives one hydraulic pump (9A'" and 9B'"), whereby each of these two pumps is connected to a respective independent hydraulic system (10B'" and 10C'"). Moreover, an electric motor driven hydraulic pump (11A'") provides primary hydraulic power to a third hydraulic system (10A'"), also in normal operation. In order to provide emergency power, the third hydraulic system (10A'") is connected to a ram air turbine driven hydraulic pump (7'"), which provides emergency hydraulic power to a further hydraulic motor (6'") that is also connected to the third hydraulic circuit (10A'") and is further mechanically connected to an emergency power generator, which in turn provides emergency electrical power to the emergency AC power bus AC ESS (3E'") which provides power to the critical or essential electrical components. Furthermore, similarly to the above arrangement of FIG. 2, a hydraulic power transfer unit (121'") is connected between the two hydraulic circuits (10B'" and 10C'") to selectively transfer hydraulic power in either one of two directions between the two independent hydraulic systems (10B'" and 10C'"). This hydraulic power transfer unit may, for example, replace an electric motor driven hydraulic pump in the hydraulic circuit, as described above with reference to FIG. 1.
However, the present configuration may further include an electric motor driven hydraulic pump (11B'") to provide hydraulic power boost or the like.
As a general summary, it is noted that all three of the above described variants of a hydraulic and electrical on-board energy system of a vehicle each include the redundant systems or devices that will now be generally discussed, and that serve the same functions and purposes in the various alternative systems but are merely arranged and interconnected in different configurations relative to the individual hydraulic circuits and electrical buses in the three different alternative systems. In this context, plural pressure regulated hydraulic pumps driven by electric motors are used for producing the necessary hydraulic power for normal ground operation or alternative operation of the vehicle such as an air-craft. In individual cases, these hydraulic pumps can also be connected to the hydraulic circuit to act as primary pumps in normal operation or as an alternative. Thereby, electrical energy is converted into mechanical energy to drive a shaft or other mechanical drive train, by which the mono-functional hydraulic pumps are driven. In other words, energy is uni-directionally converted from electrical energy to mechanical energy and further to hydraulic energy. Further, these on-board energy systems include a mono-functional emergency power generator which produces emergency electrical energy using the available hydraulic energy from at least one of the hydraulic systems in the event of a failure of the primary electrical generators. Moreover, each one of the engines considered in the system configuration carries or incorporates at least one AC generator and one hydraulic pump, and the system configuration according to FIG. 2 even includes two hydraulic pumps for each engine. In this manner, the reliability and safety of the system is improved, not only by the redundancy of the available engines, but also by the redundant number of primary hydraulic and electrical energy sources, namely pumps and generators, whereby the individual availability and accessibility of the primary energy sources is also improved. In view of the above, the known system configuration necessarily include a relatively high number of partial functional systems, in order to achieve a high power supply reliability of both the hydraulic energy system and the electrical energy system, and in order to ensure safety of the installed on-board energy system by providing a constantly available source of hydraulic energy and source of electrical energy.
For the above reasons, the complexity, effort and cost of installation of such systems in vehicles like air-craft is disadvantageously high, and simultaneously the total vehicle weight and the operating costs for the vehicle with all its systems, including fuel costs, maintenance costs, and repair costs, are also disadvantageously increased. Finally, it is noted that none of the above described known systems make use of a bi-directional conversion and cross-connection of the hydraulic and electrical energy systems.